Granular form of a mixture of a nickel-quencher and a benzophenone and process for its preparation

ABSTRACT

Granular form of a mixture comprising: (a) a nickel-quencher corresponding to [2,2′-thio-bis(4-t-octyl-phenolate)-n-butylamine Nickel (II)]; (b) a 2-hydroxy-4-alkyloxybenzophenone corresponding to 2-hydroxy-4-n-octyloxybenzophenone; characterized in that it has two diffraction lines at angles 2θ=17.593 and 2θ=22.023 in the X-Ray diffraction spectrum from powders. The above granular form can be used as a light stabilizer for agricultural films based on polyolefins or olefinic copolymers.

The present invention relates to a granular form of a mixture of anickel-quencher and a benzophenone.

More specifically, the present invention relates to a granular form of amixture of a nickel-quencher and a 2-hydroxy-4-alkyloxybenzophenone, aprocess for its preparation and its use as a light stabilizer foragricultural films based on polyolefins or olefinic copolymers.

The present invention also relates to agricultural films based onpolyolefins or olefinic copolymers stabilized with the above granularform and greenhouses covered with these films.

Nickel-quenchers are at present sold in fine powder form and their usecauses problems of environmental pollution, health and the safety of theoperators in the feeding and handling phase.

A benzophenone is also generally used in the stabilization ofagricultural films, together with nickel-quenchers.

Conventional methods for obtaining a physical form of nickel-quencherwith a low powder content (for example, compaction of the powders underpressure) tested on both the nickel-quencher alone, and on mixtures ofnickel-quenchers and benzophenones, have proved to be inapplicable orhave not given satisfactory results.

The Applicant has now found a granular form of a mixture of anickel-quencher and a benzophenone capable of overcoming the drawbacksof the known art.

The present invention therefore relates to a granular form of a mixturecomprising:

(a) a nickel-quencher corresponding to[2,2′-thio-bis(4-t-octyl-phenolate)-n-butylamineNickel (II)] havingformula (I):

(b) a 2-hydroxy-4-alkyloxybenzophenone corresponding to2-hydroxy-4-n-octyloxybenzophenone having formula (II):

 characterized in that it has two diffraction lines at angles 2θ=17.593and 2θ=22.023 in the X-Ray diffraction spectrum from powders.

The X-Ray diffraction spectrum from powders is carried out usingCu-K_(α) radiation (λ=1.54178).

In the granular form of the present invention, the nickel-quencher (a)having formula (I) and the benzophenone (b) having formula (II) are usedin a ratio ranging from 0.4 to 3, preferably in a ratio ranging from 1to 2.

The nickel-quencher (a) having formula (I) is known under the followingtrade-names: Cyasorb UV 1084 of Cytec, or Chimassorb N-705 of Ciba.

The benzophenone (b) having formula (II) is known under the followingtrade-names: Lowilite 22 of Great Lakes, Chimassorb 81 of Ciba, orCyasorb UV 531 of Cytec.

The granular form of the present invention can be obtained according tothe following process.

A process for the preparation of the granular form of the presentinvention comprises:

(1) dissolving, under stirring, the nickel-quencher (a) having formula(I) in the benzophenone (b) having formula (II) which has beenpreviously melted at 50° C.;

(2) cooling the solution obtained as described under point (1).

Step (1) of the above process is carried out at a different temperaturedepending on the ratio between the nickel-quencher (a) having formula(I) and the benzophenone (b) having formula (II), used: step (1) of thepresent invention is generally carried out at a temperature ranging from50° C. to 150° C., preferably between 50° C. and 120° C.

The cooling according to step (2) of the above process, suitable forcausing the solidification of the solution obtained as described inpoint (1), can be obtained with any of the methods known in the art.

The preferred methods consist in:

pouring the solution onto a cold metal plate maintained, for example, ata temperature equal to or less than room temperature: in this case thesolid obtained must be granulated so as to obtain granules having thedesired dimensions;

dripping the solution onto a cold metal plate maintained, for example,at a temperature equal to or less than room temperature: in this casedrops are obtained already having the desired dimensions.

The nickel-quencher (a) and benzophenone (b) powders and the granulesobtained as described above, are subjected to X-Ray diffraction and thespectra obtained are indicated in the following figures:

FIG. 1: X-Ray diffraction spectrum from powders of the nickel-quencher(a) in powder form;

FIG. 2: X-Ray diffraction spectrum from powders of benzophenone (b) inpowder form;

FIG. 3: X-Ray diffraction spectrum from powders of the physical mixtureof nickel-quencher (a) and benzophenone (b) powders;

FIG. 4: X-Ray diffraction spectrum from powders of the granulesobtained, as described above, from the mixture of nickel-quencher (a)and benzophenone (b) powders.

As can be observed, FIG. 4 shows two diffraction lines at angles2θ=17.593 and 2θ=22.023 in the X-Ray diffraction spectrum from powderswhich are not present in the X-Ray diffraction spectrum from powders ofthe nickel-quencher (a) and benzophenone (b) alone (FIG. 1 and 2) andtheir physical mixture (FIG. 3).

The granular form of the present invention has a melting range between47° C. and 50° C., measured by Buchi Instrument (tube of 1 mm ofdiameter). As an additive having a low melting point generally has ashorter homogenization time in the polymer to which it is added, it isevident that, in addition to the advantage of overcoming the drawbacksof the known art described above, the granular form of the presentinvention also guarantees a more rapid homogenization of the additivesinside the polymer. In addition, as the process for the preparation ofthe granular form of the present invention comprises, in step (a), aphase in which both compounds (a) and (b) are in the liquid state, thereis also a perfectly homogeneous distribution of the two additivestherein (for example, mechanical mixing of the two powders does notproduce a mixture having the same degree of homogeneity).

As already mentioned above, the granular form of the present inventioncan be used as a light stabilizer for agricultural films based onpolyolefins and olefinic copolymers.

Polyolefins and olefinic copolymers which can be used for the purposeare:

(1) polymers of mono-olefins and diolefins such as, for example,polypropylene, polyisobutylene, polybut-1-ene, poly-4-methylpent-1-ene,polyisoprene or polybutadiene; as well as polymers of cyclo-olefins suchas, for example, cyclopentene or norbornene; polyethylene (which can beoptionally cross-linked) such as, for example, high density polyethylene(HDPE), low density polyethylene (LDPE), linear low density polyethylene(LLDPE), branched low density polyethylene (BLDPE).

Polyolefins such as, for example the mono-olefins mentioned in the aboveparagraph, preferably polyethylene and polypropylene, can be preparedwith various methods known in literature, preferably using the followingmethods:

(a) radicalic polymerization (generally carried out at a high pressureand high temperature);

(b) catalytic polymerization using a catalyst which normally containsone or more metals of groups IVb, Vb, VIb or VIII of the Periodic Table.These metals generally have one or more ligands such as, for example,oxides, halides, alcoholates, ethers, amines, alkyls, alkenyls and/oraryls which can be π- or σ-co-ordinated. These metal complexes can be infree form or supported on substrates such as, for example activatedmagnesium chloride, titanium(III) chloride, alumina or silicon oxide.These catalysts can be soluble or insoluble in the polymerizationmedium. The catalysts can be used alone or in the presence of otheractivators such as, for example, metal alkyls, metal hydrides, halidesof metal alkyls, oxides of metal alkyls or metal alkyloxanes, thesemetals being elements belonging to groups Ia, IIa and/or IIIa of thePeriodic Table. The activators can be conveniently modified with otherester, ether, amine or silyl-ether groups. These catalytic systems areusually called Phillips, Standard Oil Indiana, Ziegler (-Natta), TNZ(Du-Pont), metallocene or “single site catalyst” (SSC).

(2) Mixtures of the polymers described under point (1) such as, forexample, mixtures of polypropylene with polyisobutylene; mixtures ofpolypropylene with polyethylene (for example, PP/HDPE, PP/LDPE);mixtures of different types of polyethylene (for example, LDPE/HDPE).

(3) Copolymers of mono-olefins and diolefins with each other or withother vinyl monomers such as, for example, ethylene-propylenecopolymers, linear low density polyethylene (LLDPE) and its mixtureswith low density polyethylene (LDPE), propylene/but-1-ene copolymers,propylene/isobutylene copolymers, ethylene/but-1-ene copolymers,ethylene/hexene copolymers, ethylene/methylpentene copolymers,ethylene/heptene copolymers, ethylene/octene copolymers,propylene/butadiene copolymers, isobutylene/isoprene copolymers,ethylene/alkyl acrylate copolymers, ethylene/alkyl methacrylatecopolymers, ethylene/vinyl acetate copolymers and their copolymers withcarbon monoxide or ethylene/acrylic acid copolymers and their salts(ionomers) as well as terpolymers of ethylene with polypropylene and adiene such as, for example, hexadiene, dicyclopentadiene orethylidene-norbornene; and mixtures of these copolymers with each otheror with the polymers cited in paragraph (1) such as, for example,polypropylene/ethylene-propylene copolymers, LDPE/ethylene-vinylacetate(EVA) copolymers, LDPE/ethylene-acrylic acid (EAA) copolymers,LLDPE/EVA, LLDPE/EAA, and alternating or random polyalkylene/carbonmonoxide copolymers and their mixtures with other polymers such as, forexample, polyamides.

Preferred for the purpose are polymers of mono-olefins, preferablyα-mono-olefins such as, for example, polypropylene, polyisobutylene,polybut-1-ene, poly-4-methylpent-1-ene, as well as polymers ofcyclo-olefins, polyethylene (which can be optionally cross-linked) suchas, for example, high density polyethylene (HDPE), low densitypolyethylene (LDPE), linear low density polyethylene (LLDPE), branchedlow density polyethylene (BLDPE) and copolymers of these monomers withvinyl acetate. Even more preferred are polyethylene, ethylene/propylenecopolymer, ethylene/vinyl acetate copolymer and polypropylene, inparticular polyethylene, preferably low density polyethylene (LDPE).

A further object of the present invention relates to agricultural filmsbased on polyolefins or olefinic copolymers containing an effectivequantity of the granular form described above.

The granular form of the present invention can be used as such orcombined with other stabilizers, in the above polymeric agriculturalfilms.

The granular form of the present invention is generally used in aquantity ranging from about 0.1% to about 2% with respect to the weightof the films to be stabilized, preferably between about 0.2% and about1%.

The granular form of the present invention, optionally in the presenceof other additives, can be easily incorporated into the polymers to bestabilized using the conventional techniques.

The resulting polymeric compositions can be transformed into filmsoperating according to the conventional techniques.

The above films based on polyolefins or olefinic copolymers, can containmetal oxides or hydroxides such as, for example, oxides of zinc,aluminum, calcium or magnesium, or hydroxides of zinc, aluminum orcalcium, preferably zinc oxide (ZnO), zinc hydroxide [Zn(OH)₂], aluminumortho- or meta-hydroxide [Al (OH)₃], aluminum α- or γ-oxide, magnesiumoxide (MgO) Zinc oxides or hydroxides are preferred, zinc oxide is evenmore preferred.

The above metal oxides or hydroxides are generally added in a quantityranging from 0.005% to 3% by weight with respect to the weight of thefilms to be stabilized, preferably between 0.005% and 1% by weight, evenmore preferably between 0.025% and 0.5% by weight.

In many cases, the above films contain a salt of a C₁-C₃₀ carboxylicacid, preferably a salt of a C₈-C₂₂ carboxylic acid, even morepreferably a salt of a C₈-C₁₈ carboxylic acid.

Preferred films are those which contain one or more components selectedfrom salts of earth-alkaline metals, zinc salts and aluminum salts of aC₁-C₃₀ carboxylic acid, hydrotalcites, and sterically hindered amines.

Films based on polyolefins or olefinic copolymers containing salts of aC₁-C₃₀ carboxylic acid are of greatest interest for the purpose. Metalcarboxylates which can be optionally added are, mainly, salts of Al, Ba,Ca, Mg, Sr or Zn. Salts of Al, Ca, Mg or Zn, especially of C₁₂-C₁₈ iscarboxylic acids, are preferred. Calcium salts such as, for example,calcium stearate, are even more preferred.

The metal carboxylates are used in a quantity ranging from 0.05% to 2%by weight with respect to the weight of the films to be stabilized,preferably between 0.1% and 1% by weight.

The sterically hindered amines are added in a quantity ranging fromabout 0.01% to 5% by weight with respect to the weight of the films tobe stabilized, preferably between 0.025% and 2% by weight, even morepreferably between 0.05% and 1% by weight.

The films described above may advantageously contain a hydrotalcite.Hydrotalcites which can be used for the purpose are selected from thosehaving the following general formula (III):

 M²⁺ _(1−x).M³⁺ _(x).(OH)₂.(A^(n−))_(x/n).pH₂O  (III)

wherein:

M²⁺ is Mg, Ca, Sr, Ba, Zn, Pb, Sn and/or Ni;

M³⁺ is Al, B or Bi;

A^(n−) is an anion of the valency n;

n is a number between 1 and 4 extremes included;

x is a number between 0 and 0.5 extremes included;

p is a number between 0 and 2 extremes included;

A is OH⁻, Cl⁻, Br⁻, I⁻, ClO₄ ⁻, HCO₃ ⁻, CH₃COO⁻, C₆H₅COO⁻ CO₃ ²⁻, SO₄²⁻, (COO)₂ ²⁻, (CHOHCOO)²⁻ ², (CHOH)₄CH₂OHCOO⁻, C₂H₄(COO)₂ ²⁻, (CH₂COO)₂²⁻, CH₃CHOHCOO⁻, SiO₃ ²⁻, SiO₄ ⁴⁻, Fe(CN)₆ ³⁻, Fe(CN)₆ ⁴⁻, BO₃ ³⁻, PO₃³⁻ or HPO⁴ ²⁻.

Preferred hydrotalcites having general formula (III) are those whereinM²⁺ is Ca²⁺, Mg²⁺ or a mixture of Mg²⁺ and Zn²⁺, A^(n−) is CO₃ ²⁻, BO₃³⁻ or PO₃ ³⁻, x is a number between 0 and 0.5 extremes included and p isa number between 0 and 2 extremes included.

Other hydrotalcites which can be advantageously used are those havinggeneral formula (IIIa):

M_(x) ²⁺Al₂(OH)_(2x+6nz)(A^(n−))₂.pH₂O  (IIIa)

wherein:

M²⁺ is Mg or Zn, preferably Mg;

A^(n−) is an anion selected from CO₃ ²⁻, (COO)₂ ²⁻, OH⁻ and S²⁻, whereinn is the valency of the anion.

p is a positive number, preferably between 0 and 5 extremes included,for example between 0.5 and 5 extremes included;

x is a positive number preferably between 2 and 6 extremes included;

z is a positive number less than 2.

Preferred hydrotalcites having general formula (IIIa) are thoserepresented by the following formulae (IIIb)-(IIIh):

Al₂O₃.6MgO.CO₂.12H₂O  (IIIb);

Mg_(4.5)Al₂(OH)₁₃.CO₃.3.5H₂O  (IIIc);

4MgO.Al₂O₃.CO₂.9H₂O  (IIId);

4MgO.Al₂O₃.CO₂.6H₂O  (IIIe);

ZnO.3MgO.Al₂O₃.CO₂.8-9H₂O  (IIIf);

ZnO.3MgO.Al₂O₃.CO₂.5-6H₂O  (IIIg);

Mg_(4.5)Al₂(OH)₁₃.CO₃  (IIIh).

Hydrotalcites can be advantageously used in a quantity ranging from0.0l% to 5% by weight with respect to the weight of the films to bestabilized, preferably between 0.2% and 3% by weight.

Useful sterically hindered amines which can be added to the filmsdescribed above, can be single compounds or mixtures of compounds. Inthe case of mixtures, the quantities indicated above refer to the totalquantity of sterically hindered amines used.

Sterically hindered amines refer to compounds containing one or moretrivalent groups having general formula (IV):

wherein G is hydrogen or methyl and not more than one of the freevalencies in the above general formula (IV) is saturated with a hydrogenand 2 or 3 of the free valencies represent bonds with carbon atoms orhetero-atoms.

Examples of the above sterically hindered amines are described, forexample, in U.S. Pat. Nos. 4,086,204, 4,108,829, 4,263,434, 4,233,412,4,288,593, 4,315,859, 4,321,374, 4,331,586, 4,413,093, 4,435,555,4,477,615, 4,335,242, 4,376,836, 4,433,145, 4,459,395, 4,477,615,4,533,688, 4,540,728, 4,547,548 and 4,740,544; in European patentapplications EP 22,080, EP 29,522, EP 24,338, EP 42,554, EP 44,499, EP70,386, EP 72,009, EP 75,849, EP 82,244, EP 94,048, EP 107,615, EP402,889 and EP 357,223; and in German patent application DE 3,530,666;the texts of the above documents should be considered as forming anintegrant part of the present description.

In many cases, the sterically hindered amines are cyclic, in particularthey are compounds selected from polyalkylpiperidine derivativescontaining at least one group having general formula (V):

wherein G is hydrogen or methyl, and G₁ and G₂ are hydrogen, methyl or,together, they are a substituent=0; the polyalkylpiperidine groupshaving general formula (V) are generally substituted in position 4 byone or two polar substituents or by a polar ring having a spirostructure.

Of particular importance are cyclic stearically hindered aminescontaining at least one group having genera formula (V) where G ishydrogen and G₁ and G₂ are hydrogen or, together, are substituent=0.

In particular, derivatives of 2,2,6,6-tetramethylpiperidine areadvantageously used.

Of particular importance is the use of compounds belonging to the groupof polyalkylpiperidine carrying at least one group having generalformula (V) in the molecule, selected from those listed below underpoints (a)-(i).

(a) Compounds having general Formula (VI):

Wherein n is a number between 1 and 4 extremes included; G and G₁ are,each independently, hydrogen or methyl; G₁₁ is hydrogen, a C₁-C₁₈ alkylgroup, a C₃-C₈ alkenyl group, a C₃-C₈ alkinyl group, a C₁₇-C₁₂ aralalkylgroup, a C₁-C₈ alkanoyl group, a C₃-C₅ alkenoyl group, a glycidyl group,a —CH₂CH(OH)—Z group wherein Z is hydrogen, methyl, or phenyl, G₁₁preferably being hydrogen, a C₁-C₄ alkyl group, an allyl, a benzyl, anacetyl or an acryloyl; G₁₂, when n is 1, is hydrogen, a C₁-C₁₈ alkylgroup which can be interrupted by one or more oxygen atoms, a cyanoethylgroup, a benzyl, a glycidyl group, a monovalent radical of a carboxylicacid, of a carbamic acid or of an acid containing phosphorous,aliphatic, cycloaliphatic or araliphatic, unsatured or aromatic, or amonovalent silyl radical, preferably a radical of an aliphaticcarboxylic acid having from 2 to 18 carbon atoms, of a cycloaliphaticcarboxylic acid having from 7 to 15 carbon atoms, of an α,β-unsaturatedcarboxylic acid having from 3 to 5 carbon atoms, of an aromaticcarboxylic acid having from 7 to 15 carbon atoms, said carboxylic acidsoptionally substituted in the aliphatic, cycloaliphatic or aromatic partwith 1-3 —COOZ₁₂ groups wherein Z₁₂ is hydrogen, a C₁-C₂₀ alkyl group, aC₃-C₁₂ alkenyl group, a C₅-C₇ cycloalkyl group, a phenyl or a benzyl;G₁₂, when n is 2, is a C₂-C₁₂ alkylene group, a C₄-C₁₂ alkenyienicgroup, a xylylene group, a divalent radical of a dicarboxylic acid, of adicarbamic acid or of an acid containingphosphorous, aliphatic,cycloaliphatic, araliphatic or aromatic, or a divalent silyl radical,preferably a radical of an aliphatic dicarboxylic acid having from 2 to36 carbon atoms, of a cycloaliphatic or aromatic dicarboxylic acidhaving from 8 to 14 carbon atoms, of an aliphatic, cycloaliphatic oraromatic dicarbamic acid having from 8 to 14 carbon atoms, saiddicarboxylic acids optionally substituted in the aliphatic,cycloaliphatic or aromatic part, with 1 or 2 —COOZ₁₂ groups wherein Z₁₂has the same meanings described above; G₁₂, when n is 3, is a trivalentradical of an aliphatic, cycloaliphatic or aromatic tricarboxylic acid,optionally substituted in the aliphatic, cycloaliphatic or aromaticpart, with a —COOZ₁₂ group wherein Z₁₂ has the same meanings describedabove, or of an aromatic tricarbamic acid or of an acid containingphosphorous, or it is a trivalent silyl radical; G₁₂, when n is 4, is atetravalent radical of an aliphatic, cycloaliphatic or aromatictetracarboxylic acid.

Radicals of tetracarboxylic acids comprise, in any case, radicals havingthe formula (—CO)_(n)R wherein n has the same meaning defined above andR can be easily deduced from the definition described above.

Examples of C₁-C₁₂ alkyl groups are: methyl, ethyl, n-propyl, n-butyl,sec-butyl, t-butyl, n-hexyl, n-octyl, 2-ethylhexyl, n-nonyl, n-decyl,n-undecyl, n-dodecyl, etc.

Examples of G₁₁ and G₁₂ substituents, when they are a C₁-C18 alkylgroup, are, in addition to the groups described above: n-tridecyl,n-tetradecyl, n-hexadecyl, n-octadecyl, etc.

Examples of the substituent G₁₁, when it is a C₃-C₈ alkenyl group, are:1-propenyl, allyl, methallyl, 2-butenyl, 2-pentenyl, 2-hexenyl,2-octenyl, 4-t-butyl-2-butenyl, etc.

When the substituent G₁₁ is a C₃-C₈ alkinyl group, it is preferablypropargyl.

When the substituent G₁₁ is a C₇-C₁₂ aralalkyl group, it is inparticular phenethyl, preferably benzyl.

Examples of the substituent G₁₁, when it is a C₁-C₈ alkanoyl group, are:formyl, propionyl, butyryl, octanoyl, preferably acetyl and, when it isa C₃-C₅ alkenoyl group, preferably acryloyl.

Examples of the substituent G₁₂, when it is a monovalent radical of acarboxylic acid, are radicals of the following acids: acetic, caproic,stearic, acrylic, methacrylic, benzoic,β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic, etc.

Examples of the substituent G₁₂, when it is a monovalent silyl radical,are: a radical having the general formula —(C_(j)H_(2j))—Si(Z′)₂Z″wherein j is an integer between 2 and 5 extremes included, and Z′ and Z″are, each independently, a C₁-C₄ alkyl group or a C₁-C₄ alkoxyl group.

Examples of the substituent G₁₂, when it is a divalent radical of adicarboxylic acid, are radicals of the following acids: malonic,succinic, glutaric, adipic, suberic, sebacic, maleic, itaconic,phthalic, dibutylmalonic, dibenzylmalonic,butyl(3,5-di-tert-butyl-4-hydroxybenzyl)malonic,bicycloheptenedicarboxylic, etc.

Examples of the substituent G₁₂, when it is a trivalent radical of atricarboxylic acid, are radicals of the following acids: trimellitic,citric, nitrilotriacetic, etc.

Examples of the substituent G₁₂, when it is a tetravalent radical of atetracarboxylic acid, are radicals of the following acids:butane-1,2,3,4-tetracarboxylic, pyromellitic, etc.

Examples of the substituent G₁₂, when it is a divalent radical of adicarbamic acid, are radicals of the following acids:hexamethylenedicarbamic, 2,4-toluylenedicarbamic, etc.

Compounds having general formula (VI) are preferred, wherein G ishydrogen, G₁₁ is hydrogen or methyl, n is 2 and G₁₂ is a diacyl radicalof an aliphatic dicarboxylic acid having from 4 to 12 carbon atoms.

Specific examples of polyalkylpiperidines having general formula (VI)are:

1) 4-hydroxy-2,2,6,6-tetramethylpiperidine;

2) 1-allyl-4-hydroxy-2,2,6,6-tetramethylpiperidine;

3) 1-benzyl-4-hydroxy-2,2,6,6-tetramethylpiperidine;

4) 1-(4-t-butyl-2-butenyl)-4-hydroxy-2,2,6,6-tetramethylpiperidine;

5) 4-stearyloxy-2,2,6,6-tetramethylpiperidine;

6) 1-ethyl-4-salicyloyloxy-2,2,6,6-tetramethylpiperidine;

7) 4-methacryloyloxy-1,2,2,6,6,-pentamethylpiperidine;

8)1,2,2,6,6-pentamethylpiperidin-4-yl-β-(3,5-di-t-butyl-4-hydroxyphenyl)propionate;

9) di(1-benzyl-2,2,6,6-tetramethylpiperidin-4-yl)maleate;

10) di(2,2,6,6-tetramethylpiperidin-4-yl)succinate;

11) di(2,2,6,6-tetramethylpiperidin-4-yl)glutarate;

12) di(2,2,6,6-tetramethylpiperidin-4-yl)adipate;

13) di(2,2,6,6-tetramethylpiperidin-4-yl)sebacate;

14) di(1,2,2,6,6-pentamethylpiperidin-4-yl)sebacate;

15) di (1,2,3,6 -tetramethyl-2,6-diethylpiperidin-4-yl)sebacate;

16) di(1-alyl-2,2,6,6-tetramethylpiperidin-4-yl)phthalate;

17) (1-acetyl-2,2,6,6-teramethylpiperidin-4-yl)acetate;

18) ester of tri(2,2,6,6-tetramethylpiperidin-4-yl) trimellitic acid;

19) 1-acryloyl-4-benzyloxy-2,2,6,6-tetramethylpiperidine;

20) di(2,2,6,6-tetramethylpiperidin-4-yl)diethylmalonate;

21) di(1,2,2,6,6-pentamethylpiperidin-4-yl)dibutylmalonate;

22)di(1,2,2,6,6-pentamethylpiperidin-4-yl)butyl-(3,5-di-tert-butyl-4-hydroxybenzyl)malonate;

23)hexane-1′,6′-bis(4-carbamoyloxy-1-n-butyl-2,2,6,6-tetramethylpiperidine;

24)toluene-2′,4′-bis(4-carbamoyloxy-1-n-propyl-2,2,-6,6-tetramethylpiperidine;

25) dimethyl-bis(2,2,6,6-tetramethylpiperidin-4-oxy)silane;

26) phenyl-tris(2,2,6,6-tetramethylpiperidin-4-oxy)silane;

27) tris(1-propyl-2,2,6,6-tetramethylpiperidin-4-yl)phosphite;

28) tris(1-propyl-2,2,6,6-tetramethylpiperidin-4-yl)phosphate;

29) bis(1,2,2,6,6-pentamethylpiperidin-4-yl)phenylphosponate;

30) 4-hydroxy-1,2,2,6,6,-pentamethylpiperidine;

31) 4-hydroxy-N-hydroxyethyl-2,2,6,6,-tetramethylpiperidine;

32) 4-hydroxy-N-(2-hydroxypropyl)-2,2,6,6-tetramethylpiperidine;

33) 1-glycidyl-4-hydroxy-2,2,6,6-tetramethylpiperidine.

(b) Compounds having general formula (VII):

wherein n is 1 or 2; G, G₁ and G₁₁ have the same meanings defined underpoint (a); G₁₃ is hydrogen, a C₁-C₁₂ alkyl group, a C₂-C₅ hydroxyalkylgroup, a C₅-C₇ cycloalkyl group, a C₇-C₈ aralalkyl group, a C₂-C₁₈alkanoyl group, a C₃-C₅ alkenoyl group, a benzoyl group, or a grouphaving the following general formula:

wherein G, G₁ and G₁₁ have the same meanings defined under point (a);G₁₄, when n is 1, is hydrogen, a C_(1-C) ₁₈ alkyl group, a C₃-C₈ alkenylgroup, a C₅-C₇ cycloalkyl group, a C₁-C₄ alkyl group substituted with ahydroxyl group, with a cyano group, with an alkoxycarbonyl group or witha carbamide group, a glycidyl group, a group having the formula—CH₂—CH(OH)—Z or having the formula —CONH—Z wherein Z is hydrogen,methyl or phenyl;

G₁₄, when n is 2, is a C₂-C₁₂ alkylene group, a C₆-C₁₂ arylene group, axylylene group, a group having the formula —CH₂—CH(OH)—CH₂— or havingthe formula —CH₂—CH(OH)—CH₂—O—D—O— wherein D is a C₂-C₁₀ alkylene group,a C₆-C₁₅ arylene group, a C₆-C₁₂ cycloalkylene group; or, on thecondition that G₁₃ is not an alkanoyl group, an alkenoyl group or abenzoyl group, G₁₄ can also be a 1-oxo-(C₂-C₁₂)-alkylene group, adivalent radical of a dicarboxylic acid or of a dicarbamic acid,aliphatic, cycloaliphatic or aromatic, or also a —CO— group;

or, when n is 1, G₁₃ and G₁₄ together can also be a divalent radical ofa 1,2- or 1,3-dicarboxylic acid, aliphatic, cycloaliphatic or aromatic.

The term aryl refers to an aromatic hydrocarbon such as, for example,phenyl or naphthyl. The term aralkyl refers to an alkyl substituted withan aromatic hydrocarbon, for example, a hydrocarbon having from 6 to 10carbon atoms; examples of aralkyls are benzyl, α-methylbenzyl, etc.

C₁-C₁₂ alkyl or C₁-C18 alkyl groups have already been defined underpoint (a).

C₅-C₇ cycloalkyl groups are, preferably, cyclohexyl.

When G₁₃ is a C₇-C₈ aralkyl group, it is phenylethyl, preferably benzyl.

When G₁₃ is a C₂-C₅ hydroxyalkyl group, it is 2-hydroxyethyl,2-hydroxypropyl, etc.

Examples of G₁₃, when it is a C₂-C₁₈ alkanoyl group, are: propionyl,butyryl, octanoyl, dodecanoyl, hexadecanoyl, octadecanoyl, etc.,preferably acetyl and, when it is a C₃-C₅ alkenoyl group, preferablyacryloyl.

Examples of G₁₄, when it is a C₂-C₈ alkenyl group, are: allyl,methallyl, 2-butenyl, 2-pentenyl, 2-hexen-yl, 2-octenyl, etc.

Examples of G₁₄, when it is a C₁-C₄ alkyl group substituted by ahydroxyl, cyano, alkoxycarbonyl or carbamide group, are: 2-hydroxyethyl,2-hydroxypropyl, 2-cyanoethyl, methoxycarbonylmethyl,2-ethoxycarbonyl-ethyl, 2-aminocarbonylpropyl,2-(dimethylaminocarbonyl)ethyl, etc.

Examples of C₂-C₁₂ alkylene groups are: ethylene, propylene,2,2-dimethylpropylene, tetramethylene, hexamethylene, octamethylene,decamethylene, dodecamethylene, etc.

Examples of C₆ -C₁ arylene groups are: o- m- or p-phenylene,1,4-naphthylene, 4,4′-diphenylene, etc.

Examples of C₆-C₁₂ cycloalkylene groups are, preferably, cyclohexylene.

Preferred compounds having general formula (VIII) are those wherein n is1 or 2, G is hydrogen, G₁₁ is hydrogen or methyl, G₁₃ is hydrogen, aC₁-C₁₂ alkyl group or a group having the formula:

and G₁₄, when n is 1, is hydrogen or a C₁-C₁₂ alkyl group and, when n is2, is a C₂-C₈ alkylene group or a 1-oxo-C₂-C₈ alkylene group.

Specific examples of polyalkylpiperidines having general formula (VII)are:

1) N,N′-bis(2,2,6,6-tetramethylpiperidin-4-yl)hexamethylene-1,6-diamine;

2)N,N′-bis(2,2,6,6-tetramethylpiperidin-4-yl)hexamethylene-1,6-diacetamide;

3) Bis (2,2,6,6-tetramethylpiperidin-4-yl)amine;

4) 4-benzoylamino-2,2,6,6-tetramethylpiperidine;

5) N,N′-bis(2,2,6,6-tetramethylpiperidin-4-yl)-N,N′-dibutyladipamide;

6)N,N′-bis(2,2,6,6-tetramethylpiperidin-4-yl)-N,N′-dicyclohexyl-2-hydroxypropylene-1,3-diamine;

7) N,N′-bis(2,2,6,6-tetramethylpiperidin-4-yl)-p-xylylenediamine;

8) N,N′-bis(2,2,6,6-tetramethylpiperidin-4-yl) succinediamide;

9)Bis(2,2,6,6-tetramethylpiperidin-4-yl)-N-(2,2,6,6-tetramethylpiperidin-4-yl)-β-aminodipropionate;

10) Compounds having the formula:

11) 4-[bis(2-hydroxyethyl)amino]-1,2,2,6,6-pentamethylpiperidine;

12)4-(3-methyl-4-hydroxy-5-tert-butylbenzamido)-2,2,6,6-tetramethylpiperidine;

13) 4-methacrylamido-1,2,2,6,6-pentamethylpiperidine.

c) Compounds having general formula (VIII):

wherein n is 1 or 2; G, G₁ and G₁₁ have the same meanings describedunder point (a); G₁₅, when n is 1, is a C₂-C₈ alkylene orhydroxyalkylene group, or a C₄-C₂₂ acyloxyalkylene group, and, when n is2, is a (—CH₂)₂C(CH₂—)₂ group.

Examples of G₁₅ when it is a C₂-C₈ alkylene or hydroxyalkylene group,are: ethylene, 1-methylethylene, propylene, 2-ethylpropylene,2-ethyl-2-hydroxymethyl-propylene, etc.

An example of G₁₅, when it is a C₄-C₂₂ acyloxyalkylene group is2-ethyl-2-acetoxymethylpropylene.

Specific examples of polyalkylpiperidines having general formula (VIII)are:

1) 9-aza-8,8,10,10-tetramethyl-1,5-dioxaspiro[5.5]undecane;

2) 9-aza-8,8,10,10-tetramethyl-3-ethyl-1,5-dioxa-spiro[5.5]undecane;

3) 8-aza-2,7,7,8,9,9-hexamethyl-1,4-dioxaspiro[4.5]-decane;

4)9-aza-3-hydroxymethyl-3-ethyl-8,8,9,10,10-penta-methyl-1,5-dioxaspiro[5.5]undecane;

5)9-aza-3-ethyl-acetoxymethyl-9-acetyl-8,8,10,10-tetramethyl-1,5-dioxaspiro[5.5]undecane;

6)2,2,6,6-tetramethylpiperidine-4-spiro-2′-(1′,3′-dioxane)-5′-spiro-5″-(1″,3″-dioxane)-2″-spiro-4′″-(2′″,2′″,6′″,6′″-tetramethylpiperidine).

d) Compounds having general formula (IXA), (IXB) and (IXC), thecompounds having general formula (IXC) being preferred:

wherein n is 1 or 2, G, G₁ and G₁₁ have the same meanings describedunder point (a) ; G₁₆ is hydrogen, a C₁-C₁₂ alkyl group, an allyl group,a benzyl, a glycidyl group or a C₂-6 alkoxyalkyl group;

G₁₇, when n is 1, is hydrogen, a C₁-C₁₂ alkyl group, a C₃-C₅ alkenylgroup, a C₇C₉ aralalkyl group, a C₅-C₇ cycloalkyl group, a C₂-C₄hydroxyalkyl group, a C₂-C₆ alkoxyalkyl group, a C₆-C₁₀ aryl group, aglycidyl group, or a group having the formula —(CH₂)_(p)—COO—Q or—(CH₂)_(p)—O—CO—Q wherein p is 1 or 2 and Q is a C₁-C₄ alkyl group or aphenyl; G₁₇, when n is 2, is a C₂-C₁₂ alkylene group, a C₄-C₁₂alkenylene group, a C₆-C₁₂ arylene group, a group having the formula—CH₂—CH(OH)—CH₂—O—D—O—CH₂—CH (OH)—CH₂— wherein D is a C₂-C₁₀ alkylenegroup, a C₆-C₁₅ arylene group, a C₆-C₁₂ cycloalkylene group, or a grouphaving the formula —CH₂CH(OZ′)CH₂—(OCH₂—CH(OZ′)CH₂)₂ wherein Z′ ishydrogen, a C₁-C₁₈ alkyl group, an allyl, a benzyl, a C₂-C₁₂ alkanoylgroup or a benzoyl; T₁ and T₂ are, each independently, a C₁-C₁₈ alkylgroup, a C₆-C₁₀ aryl group, a C₇-C₉ aralalkyl group, said groupsoptionally substituted with a halogen atom or with a C₁-C₄ alkyl group;or T₁ and T₂, considered jointly with the carbon atom to which they arebound, form a C₅-C₁₄ cycloalkane ring.

Examples of C₁-C₁₂ alkyl groups are: methyl, ethyl, n-propyl, n-butyl,sec-butyl, tert-butyl, n-hexyl, n-octyl, 2-ethylhexyl, n-nonyl, n-decyl,n-undecyl, n-dodecyl, etc.

Examples of C₁-C₁₈ alkyl groups are, in addition to those listed above:n-tridecyl, n-tetradecyl, n-hexa-decyl, n-octadecyl, etc.

Examples of C₂-C₆ alkoxyalkyl groups are: methoxy-methyl, ethoxymethyl,propoxymethyl, t-butoxymethyl, ethoxyethyl, ethoxypropyl, n-butoxyethyl,t-butoxy-ethyl, isopropoxyethyl, propoxypropyl, etc.

Examples of G₁₇, when it is a C₃-C₅ alkenylic group are: 1-propenyl,allyl, methallyl, 2-butenyl, 2-penten-yl, etc.

Examples of G₁₇, T₁ and T₂, when they are a C₇-C₉ aralkyl group are:phenethyl, preferably benzyl.

Examples of cycloalkane rings, formed by T₁ and T₂ when thesesubstituents are considered jointly with the carbon atom to which theyare bound, are: cyclopentane, cyclohexane, cyclo-octane, cyclododecane,etc.

Examples of G₁₇, when it is a C₂-C₄ hydroxyalkyl group, are:2-hydroxyethyl, 2-hydroxypropyl, 2-hydroxy-butyl, 4-hydroxybutyl, etc.

Examples of G₁₇, T₁ and T₂, when they are a C₆-C₁₀ aryl group are: α- orβ-naphtyl, optionally substituted with a halogen atom or a C₁-C₄ alkylgroup, etc.

Examples of G₁₇, when it is a C₂-C₁₂ alkylene group are: ethylene,propylene, 2,2-dimethylpropylene, tetramethylene, hexamethylene,octamethylene, decamethylene, dodecamethylene, etc.

Examples of G₁₇, when it is a C₄-C₁₂ alkenylene group are: 2-butenylene,2-pentenylene, 3-hexenylene, etc.

Examples of G₁₇, when it is a C₆-C₁₂ arylene group are: o-, m- orp-phenylene, 1,4-naphthylene, 4,4′-diphenylene, etc.

Examples of Z′, when it is a C₂-C₁₂ alkanoyl group are: propionyl,butyryl, octanoyl, dodecanoyl, preferably acetyl.

Examples of D, when it is a C₂-C₁₀ alkylene group, a C₆-C₁₅ arylenegroup or a C₆-C₁₂ cycloalkylene group are defined above under point (b).

Specific examples of polyalkylpiperidines having general formula (IX)are:

1) 3-benzyl-1,3,8-triaza-7,7,9,9-tetramethylspiro-[4.5]decane-2,4-dione;

2)3-n-octyl-1,3,8-triaza-7,7,9,9-tetramethylspiro-[4.5]decane-2,4-dione;

3)3-allyl-1,3,8-triaza-1,7,7,9,9-pentamethylsniro-[4.5]decane-2,4-dione;

4)3-glycidyl-1,3,8-triaza-7,7,8,9,9-pentamethyl-spiro[4.5]decane-2,4-dione;

5) 1,3,7,7,8,9,9-heptamethyl-1,3,8-triazaspiro[4.5]-decane-2,4-dione;

6)2-isopropyl-7,7,9,9-tetramethyl-1-oxa-3,8-diaza-4-oxospiro[4.5]decane;

7)2,2-dibutyl-7,7,9,9,-tetramethyl-1-oxa-3,8-diaza-4-oxospiro[4.5]decane;

8)2,2,4,4-tetramethyl-7-oxa-3,20-diaza-21-oxodispiro[5.1.11.2]heneicosane;

9) 2-butyl7,7,9,9-tetramethyl-1-oxa-4,8-diaza-3-oxospiro[4.5]decane;and, preferably,

10)8-acetyl-3-dodecyl-1,3,8-triaza-7,7,9,9-tetra-methylspiro[4.5]decane-2,4-dione;

or a compound having one of the following formulae:

(e) Compounds having general formula (X):

wherein n is 1 or 2, and G₁₈ is a group having one of the followingformulae:

wherein G and G₁₁ have the same meanings described under point (a); G₁and G₂ are hydrogen, methyl, or together from a substituent=0, E is —0or —NG₁₃—;

A is a C₂₋₆ alkylene group or a —(CH₂)₃—0— group;

x is 0 or 1; G₁₃ is hydrogen, a C₁-C₁₂ alkyl group, a C₂-C₅ hydroxyalkylgroup, a C₅-C₇ cycloalkyl group;G₁₉ has the same meanings as G₁₈ or isone of the following groups: —NG₂₁G₂₂, —OG₂₃, —NHCH₂OG₂₃ or—N(CH₂OG₂₃)₂; G₂₀, when n is 1, has the same meanings as G₁₈ or G₁₉ and,if n is 2, it is an -E-B-E- group wherein B is a C₂-C₈ alkylene groupoptionally interrupted by 1 or 2 —N(G₂₁)— groups; G₂₁ is a C₁-C₁₂ alkylgroup, a cyclohexyl group, a benzyl, a C₁-C₄ hydroxyalkyl group, or agroup having the following general formula:

G₂₂ is a C₁-C₁₂ alkyl group, a cyclohexyl group, a benzyl, a C₁-C₄hydroxyalkyl group;G₂₃ is hydrogen, a C₁-C₁₂ alkyl group, a phenyl, orG₂₁ and G₂₂ together are a C₄-C₅ alkylene or oxyalkylene group , forexample:

or a group having the formula:

G₂₁ is a group having the general formula:

Examples of C₁-C₁₂ alkyl groups are: methyl, ethyl, n-propyl, n-butyl,sec-butyl, t-butyl, n-hexyl, n-octyl, 2-ethylhexyl, n-nonyl, n-decyl,n-undecyl, n-dodecyl, etc.

Examples of C₁-C₄ hydroxyalkyl groups are: 2-hy-droxyethyl,2-hydroxypropyl, 3-hydroxypropyl, 2-hydroxybutyl, 4-hydroxybutyl, etc.

Examples of A, when it is a C₂-C₆ alkylene group are: ethylene,propylene, 2,2-dimethylpropylene, tetramethylene, hexamethylene, etc.

Examples of G₂₁ and G₂₂, when they jointly form a C₄-C₅ alkylene oroxyalkylene group, are: tetramethylene, pentamethylene,3-oxaoentamethylene, etc.

Specific examples of polyalkylpiperidines having general formula (X)are:

wherein R is:

wherein R is:

wherein R is:

(f) Oligomeric or polymeric compounds whose recurrent structural unitcontains a 2,2,6,6-tetramethyl-piperidine radical having general formula(V), in particular polyesters, polyethers, polyamides, polyamines,polyurethanes, polyureas, polyamino-triazines, poly(meth)acrylates,poly(meth)acry-lamides, and their copolymers containing said radical.

Specific examples of the above 2,2,6,6-polyalkyl-piperidines arerepresented by the following formulae wherein m is a number between 2and 200:

wherein R is:

wherein m′ and m″ are an integer between 0 and 200 extremes included, onthe condition that m′+m″ is m.

Further examples of light stabilizers which can be used for the purposeare:

the reaction products between compounds having formula (XII):

 and epichlorohydrin;

polyesters obtained by the reaction of butane-1,2,3,4-tetracarboxylicacid with a bifunctional alcohol having formula (XIII):

 Whose carboxylic termination generated by tetracarboxylic acid has beenesterified with a 2,2,-6,6-tetramethyl-4-hydroxypiperidine group;

compounds having general formula (XIV):

 wherein about a third of the R radicals represent a —C₂H₅ group and theremaining a group having the formula:

 and m is a number between 2 and 200 extremes included;

copolymers whose recurrent unit consists of two units having theformula:

 a unit having the formula:

 and a unit having the formula:

(g) Compounds having general formula (XVIII):

wherein G, G₁ and G₁₁ have the same meanings described above under point(a). Compounds having general formula (XVIII) wherein G is hydrogen andG₁₁ is hydrogen or methyl, are preferably used.

Specific examples of compounds having general formula (XVIII) are:

2,2,6,6-tetramethyl-4-piperidone (triacetoneamine);

1,2,2,6,6-pentamethyl-4-piperidone;

2,3,6-trimethyl-2,6-diethyl-4-piperidone.

(h) Compounds having general formula (XIX):

wherein G₁₁ has the same meanings described above under point (a) andG₂₅ is a direct bond, a methylene or preferably a carbonyl, as describedin German patent application DE 3,530,666.

(i) Compounds having general formula (XX):

wherein R₁ is a C₁-C₁₀ alkyl group, a C₅-C₁₂ cyclo-alkyl groupoptionally substituted with a C₁-C₄ alkyl group, a phenyl optionallysubstituted with a C₁-C₁₀alkyl group; R₂ is a C₃-C₁₀alkylene group; R₃is a hydrogen, a C₁-C₈ alkyl group, 0, a —CH₂CN group, a C₃-C₆ alkenylgroup, a C₇-C₉ phenylalkyl group optionally substituted in the phenylradical with a C₁-C₄ alkyl group, a C₁-C₈ acyl group; and n₁ is a numberbetween 1 and 50 extremes included.

Specific examples of compounds having general formula (XX) are:

(1)poly-methylpropyl-3-oxy-[4-(2,2,6,6-tetramethyl)-piperidinyl]siloxane,known under the trade-name of UVASIL 299 of Great Lakes;

(2)poly-methylpropyl-3-oxy-[4-(1,2,2,6,6-pentamethyl)-piperidinyl]siloxane.

The granular formula of the present invention can be combined, asspecified above, with other conventional additives or their mixtures.These additives are added in a quantity ranging from about 0.1% to 5% byweight with respect to the weight of the films based on polyolefins orolefinic copolymers to be stabilized, preferably between 0.5% and about3% by weight.

Examples of other conventional additives which can be used are:antioxidants (such as, for example, alkylated monophenols,alkylthiomethylphenols, hydroquinones and alkylated hydroquinones,tocopherols, hydroxylated thiophenyl ethers, alkylidene-bisphenols,benzyl compounds containing O, N or S, hydroxybenzylated malonates,aromatic hydroxybenzyl compounds, triazine compounds,benzylphosphonates, acylaminophenols, esters ofβ-(3,5-di-t-butyl-4-hydroxyphenyl)propionic acid with monohydric orpolyhydric alcohols, esters of β-(5-t-butyl-4-hydroxyphenyl)propionicacid with monohydric or polyhydric alcohols, esters ofβ-(3,5-dicyclohexyl-4-hydroxyphenyl)propionic acid with monohydric orpolyhydric alcohols, esters of (3,5-di-t-butyl-4-hydroxyphenyl)aceticacid with monohydric or polyhydric alcohols, amides ofβ-(3,5-di-t-butyl-4-hydroxyphenyl)-propionic acid; other ultraviolet-rayand light stabilizers (such as, for example, derivatives of2-(2′-hydroxyphenyl)benzotriazoles, esters of benzoic acids, acrylates,oxamides, 2-(2-hydroxyphenyl)-1,3,5-triazine); “metal deactivators”;phosphites and phosphonites; agents capable of destroying peroxides;basic co-stabilizers, nucleating agents; fillers and reinforcing agents;other additives (such as, for example, plasticizers, emulsifying agents,pigments, optical brighteners, flame-retardants, antistatic agents,blowing agents, thiosynergizing agents); benzofuranones and indolinones.

The present invention also relates to a process for the stabilization ofagricultural films based on polyolefins or olefinic copolymers,particularly useful for greenhouses, comprising the incorporation of thegranular form of the present invention into the poly-olefins or olefiniccopolymers subsequently transformed into the above films. Greenhousescovered with the above agricultural films are a further object of thepresent invention.

Some illustrative but non-limiting examples are provided hereunder for abetter understanding of the present invention and for its embodiment.

EXAMPLE 1

50 g of Compound (b), corresponding to 2-hydroxy-4-n-octoxybenzophenone,are charged into a 250 ml flask equipped with a magnetic stirrer andexternally heated with an oil bath. The compound is melted (at 50° C.)and subsequently heated to about 100° C.; 100 g of Compound (a),corresponding to [2,2′-thiobis(4-t-butyloctylphenolate)-n-butyl-amineNickel (II)], are then added gradually.

Compound (a) dissolves in Compound (b) and, on heating to 120° C., aliquid mass is obtained, which is poured onto an aluminum plate cooledto about 0° C.

After about 1 hour, the solidified product is granulated by grinding,obtaining granules of the desired dimensions.

EXAMPLE 2

50 g of Compound (b), corresponding to 2-hydroxy-4-n-octoxybenzophenone,are charged into a 250 ml flask equipped with a magnetic stirrer andexternally heated with an oil bath. The compound is melted (at 50° C.)and subsequently heated to about 70° C.; 100 g of Compound (a),correspondingto [2,2′-thiobis(4-t-butyloctylphenolate)-n-butyl-amineNickel (II)], are then added gradually.

Compound (a) dissolves in Compound (b) and, maintaining a temperature of70° C., a liquid mass is obtained, which is dripped onto an aluminumplate cooled to about 0° C. After 10-15 minutes, the drops solidify andgranules of the desired dimensions are obtained.

What is claimed is:
 1. A granular form of a mixture comprising: (a) anickel-auencher corresponding to [2,2′-thiobis(4-t-octyl-phenolate)-n-butylamine Nickel (II)] having formula (I):

(b) a 2-hydroxy-4-alkyloxybenzophenone corresponding to2-hydroxy-4-n-octoloxybenzophenone having formula (II):

wherein it has two diffraction lines at angles 2θ=17.593 and 2θ=22.023in the X-ray diffraction spectrum from powders.
 2. The granular formaccording to claim 1, wherein the nickel-quencher (a) having formula (I)and the benzophenone (b) having formula (II), are used in a ratioranging from 0.4 to
 3. 3. The granular form according to claim 2,wherein the nickel-quencher (a) having formula (I) and the benzophenone(b) having formula (II), are used in a ratio ranging from 1 to
 2. 4. Aprocess for the preparation of the granular form according to claim 1,comprising: (1) dissolving, under stirring, the nickel-quencher (a)having formula (I) in the benzophen-one (b) having formula (II) whichhas been previously melted at 50° C.; (2) cooling the solution obtainedas described under point (1).
 5. The process according to claim 4,wherein step (1) is carried out at a temperature ranging from 50° C. to150° C.
 6. Agricultural films based on polyolef ins or olefiniccopolymers, containing an effective quantity of the granular formaccording to claim
 1. 7. The agricultural films according to claim 6,wherein metal oxides or hydroxides, salts of earth-alkaline metals, zincsalts and aluminum salts of a C₁-C₃₀ carboxylic acid, hydrotalcites, andsterically hindered amines, are present.
 8. A process for thestabilization of agricultural films based on polyolefins or olefiniccopolymers, comprising the incorporation of the granular form accordingto the claim 1, into the polyolefins or polyolefinic copolymerssubsequently transformed into the above films.
 9. A greenhouse coveredwith the agricultural films according to claim 1.